How to get album art ?

Hello all- I am transferring music to my 1520 using "Windows phone app for desktop" but roughly only half of my album art shows up. I know that all my album art is embedded and is there so am not sure why this is happening.
I can't seem to find an app that will let me add album art, if there is one can you please let me know of it.
My other option would be to use another music player which has the option to add art.